In recent years, research and development have been extensively conducted on light-emitting elements using electroluminescence. As a basic structure of these light-emitting elements, a structure where a substance having a light-emitting property is interposed between a pair of electrodes is used. By application of a voltage to this element, light emission from a substance having a light-emitting property can be obtained.
Since such a light-emitting element is a self-luminous element, there are advantages such as higher visibility of a pixel than visibility of a liquid crystal display, and unnecessity of a backlight. Accordingly, such a light-emitting element is considered to be suitable as a flat panel display element. In addition, such a light-emitting element can be manufactured to be thin and light, which is a great advantage. Moreover, the light-emitting element has a feature that response speed is extremely fast.
Furthermore, since such a light-emitting element can be formed into a film form, planar light emission can be easily obtained by formation of a large-area element. This characteristic is difficult to be obtained by a point light source typified by an incandescent lamp or an LED, or a line light source typified by a fluorescent lamp. Therefore, the light-emitting element has a high utility value as a plane light source that can be applied to lighting or the like.
The light-emitting elements using electroluminescence are classified roughly in accordance with whether they use an organic compound or an inorganic compound as a substance having a light-emitting property.
In a case where a substance having a light-emitting property is an organic compound, by application of a voltage to the light-emitting element, electrons and holes are injected from the pair of electrodes into the layer including an organic compound having a light-emitting property to cause current flow. Then, by recombination of these carriers (electrons and holes), the organic compound having a light-emitting property gets in an excited state, and light is emitted when the excited state returns to a ground state. Because of such a mechanism, this kind of light-emitting element is referred to as a light-emitting element of a current excitation type.
It is to be noted that an excited state formed by an organic compound can be a singlet excited state or a triplet excited state. Light emission from the singlet excited state is referred to as fluorescence, and light emission from the triplet excited state is referred to as phosphorescence.
In order to overcome many problems derived from materials of such a light-emitting element and to improve its element characteristics, improvement in an element structure, material development, and so on are carried out.
For example, anthracene derivatives have been developed as the material used for the light-emitting elements (see Reference 1: Japanese Published Patent Application No. 2003-238534). However, in order to synthesize the anthrancene derivative disclosed in Reference 1, the plurality of steps are required to be conducted. Therefore, the yield is not favorable and a long time period for synthesis is needed.